Specular Microscopy Image Quality Scale for Endothelial Cell Density Determination in Donor Cornea Tissue

Authors

Jianyan Huang, MD, PhD, Tudor C. Tepelus, PhD, Ping Huang, MD, PhD, Adam Fox, CEBT, Andrew J Maxwell, CEBT, Srinivas Sadda, MD, Olivia L. Lee, MD

Abstract

ABSTRACT
Objective: To develop an image quality rating (IQR) scale for
specular microscopy images of donor corneal endothelium and
to evaluate the accuracy and reproducibility of IQR scales based
on inter- and intra-grader variation in endothelial cell density
(ECD) values.

Methods: Using the Konan center method, we performed specular
analysis on 536 specular images of donor corneal endothelium.
All images were assessed independently for image quality
using the IQR grading scale and ECD analysis was performed by
trained specular microscopy graders.

Results: Of the 536 images, 462 (86%) were gradable (excellent,
65 [12%]; good, 230 [43%] fair, 81 [15%]; and poor, 86 [16%].
The remaining 74 (14%) were non-gradable by the image quality
scale. Inter- and intra-grader reproducibility was good (Kappa,
0.77 and 0.88, respectively). When stratified by IQR, the image
quality scale offered comparable high inter- and intra-grader repeatability
(ICC≥0.98) for ECD determination at higher image quality
ratings (excellent/good) and an acceptable confidence level
(ICC>0.8) at lower image quality ratings (fair/poor). The agreement
in ECD measurement (error<5%) is higher in excellent
(96%) and good (>83%) images, but lower in fair (>66%) and
poor (>55%) images, providing further validation of the quality
scale.

Conclusions: For trained graders, image quality is the main
factor affecting ECD reproducibility. This image quality scale
shows good reproducibility for all gradable images. Even when
the IQR score is poor, an acceptable ECD still can be provided.

Key Words: image quality rating, corneal endothelium, donor,
specular microscope